中下扬子区T1-2膏盐层位差异的构造意义

中下扬子区与华北板块碰撞时间差异是地学界讨论的热点之一。首次从构造-沉积响应的角度探讨了这一问题，这比用测年数据来研究更准确、更简便。中下扬子区在早中三叠世就开始与华北板块碰撞，碰撞引起构造抬升、相对海平面下降，形成海陆过渡的潮坪-潟湖，配以炎热干燥的气候，从而发育膏盐层。对比分析中下扬子膏盐层层位，发现下扬子膏盐层发育时代比中扬子晚8.0±3.5 Ma，从而推断下扬子的构造抬升比中扬子晚，而这种抬升正是中下扬子与华北板块的初期碰撞造成的，进一步推测下扬子与华北板块的碰撞比中扬子晚8.0±3.5 Ma。这一结论对于理解中下扬子的构造差异，明晰油气勘探思路有一定的理论意义。

TECTONICS SIGNIFICATION OF TIME DIFFERENCE OF GYPSUM-SALT LAYER IN LOWER-MIDDLE TRIASSIC IN MIDDLE-LOWER YANGTZE REGION

The time difference of collision between Middle Lower Yangtze Blocks and the North China Plate is one of the discussing points in the field of geosciences. Firstly, it is discussed from the angle of tectonic sedimentary response which is more exact and easier than the chronology data. The collision between the Middle Lower Yangtze Blocks and the North China Plate led to the Middle Lower Yangtze Blocks lifting, the relative sea level falling and tidal flat lagoons of transitional facies forming. With the dry and hot weather, gypsum salt layers were developed in the tidal flat lagoons. Comparing the gypsum salt layer time in the Middle Yangtze region and that in the Lower Yangtze region, it is found that the gypsum salt layers in the Lower Yangtze region are later about 8.0±3.5 Ma than that in the Middle Yangtze region. According to this, it can be concluded that the lifting time of the Lower Yangtze Block is later than that of the Middle Yangtze Block, which is the result of early collision between Middle Lower Yangtze Blocks and the North China Plate. So, it can be further concluded that the collision between Lower Yangtze Block and the North China Plate happened later about 8.0±3.5 Ma than that between the Middle Yangtze Block and the North China Plate. This conclusion is of significance in understanding the tectonics difference in Middle Lower Yangtze region and finding a clear way to explore oil and gas.